Niel: As an intermediate, if you have the bits, try putting a 12V computer fan on top of the oil fin heater blowing down and power it with a wall plug pack.

Pictures or it didn't happen, please?

Sorry, when I posted I was looking for the photo I took but could not find it. Had to leave early for church as I'm the sound engineer for 7 singers/musicians and thought I'll take photos later.

Keep in mind our living space has a 3m high ceiling. Before the fans you could only feel the heat by the heater and the floor was cold. With the fans blowing down the heat spreads along the floor and you get reverse convection. I can feel the fan 4m away at floor level even though it is running off 9V instead of 12V. With the fans the heater thermostat is much better at measuring room temperature rather than heater temperature. There are a few oil fin heaters on the market with a fan at the end/side, but I think the top makes much more sense. I've been running it like this for a month+. The fans do not get hot from the heater because it blows the heat down.

Did you get a heat exchanging ventilation system, or did you a dumb one that just takes cold air from the ceiling cavity and pushes it into the house, pushing the warm air out? If you got the former I suggest you only run it occasionally, not all the time, otherwise your heating bill will be huge. Heat exchanger ventilation systems that don't just throw warm air away aren't much more expensive if you go to the right place.

A better solution for wet windows is double glazing, and retrofit works just fine. It reduced my wet windows from having puddles on the window sills to having a light mist on the inside pane. Of course you need to get rid of the damp air some time, but we just run the ventilation system 10am - 4pm, while the sun's out, which heats the house.

Go to a firm who can do your a proper combined heating and ventilation system. Doing it all at once makes much more sense than doing it piecemeal. I wish I'd known that when I got my house.

It has a heat exchange/transfer system, thankfully. Still doesn't really heat the house, although it's great for cooling on hot summer nights. I'll try running it just occasionally and see what difference that makes. Thanks for the idea. We got a price for double glazing just the family room, so only one room in the house (3brm, 1 other lounge) which is more than the quote so far for central heating. Apparently we have more windows in our family room than the average whole house has. We have improved the curtains there though, and taped up against drafts, which has made a difference to that room.

It won't heat, but it just means that if you do heat it it won't throw all the heat away.

Retrofit double glazing is a lot cheaper than proper double glazing, and about 80% as effective, from memory. It's basically 3-4mm thick plastic sheets acting as a second pane of glass in your window, or alternately it can fill the whole window frame, which is more effective but perhaps uglier. It makes it easier to take out for summer though. I paid about $3000 for four rooms, each with an old style three pane window, but the company who did it isn't around any more.

timmmay: A better solution for wet windows is double glazing, and retrofit works just fine. It reduced my wet windows from having puddles on the window sills to having a light mist on the inside pane.

If you get mist on the inside then your double glazing isn't working. We have retrofitted true double glazing in all living areas, (rater expensive) but the result is amazing. We estimate we were losing about 1kw per hour of heating straight thru the glass beforehand. We now use much less electricity for heating. The double glazing is working as designed and now on humid cold mornings mists up on the outside like it's supposed too. We still get a bit of condensation inside on the aluminium frames though.

Mist or condensation is caused by the cold window causing the moisture on the inside of the pane to condense, which it does when it gets cold. No matter how good your double glazing is there will still be some heat loss, especially if it's filled with regular air, so a little condensation is to be expected.

My double glazing cost $3000 or so for four rooms, instead of $20,000 or so if we'd removed the windows and put in "proper" double glazing. Going from 500ml of water per window day to a light mist was a huge win in my opinion, and great value.

I will redo the windows with proper double glazing eventually, but there's no rush. I much prefer PCV/plastic double glazed windows to aluminium, they've used them in colder climates for many years, they don't use aluminium as it transfers heat. PVC doesn't transfer heat. I'm getting a PCV window for my bathroom during a refit for $700, 800mm x 1.2m.

timmmay: Mist or condensation is caused by the cold window causing the moisture on the inside of the pane to condense, which it does when it gets cold. No matter how good your double glazing is there will still be some heat loss, especially if it's filled with regular air, so a little condensation is to be expected.

Our glass is 2 sheets of low-e glass filled with argon between and sealed. Heat loss is very minimal compared to single glazing. According to the Sales Rep interior condensation on the glass is not possible if it works correctly. This is correct and in fact we NEVER get any condensation inside, only on the outside. Surprised me but that's the way it works. Cost around $12k for 4 rooms with exterior glass doors to balcony as well. One room was laminated for ultraviolet and sound control. Was well worth the investment cost wise. Airfoam in the walls wasw another good investment and reduced heat loss considerably as well. A dehumidifier takes car of condensation on the aluminium. Replacing with PVC wasn't an option due to cost and difficulty. I,m not sold on most of the HVR range. Doesn't work 100% all the time and still need lots of heating in wet cold conditions. Works fine in my Sister-in-Law's place in summer but boy her ceilings get really dirty round the outlets and I find the noise irritating even though it's pretty quiet. She has no heat exchanger and it just doesn't work in Winter. Give me a wood burner anytime. Had one when living in Dunedin and was excellent. Could even cook on it. Unfortunately not feasible to retrofit in my current house which is 2 storied surrounded by bush on 3 sides.

HRV does ventilation systems, not heating systems, so yes you'll need to use a heating system. I don't like HRV because their salesman who came to visit actually lied about the benefits. HRV is a brand, DVS is a brand, but DVS also stands for domestic ventilation system.

I use a timer on my ventilation system, it run 10am - 4pm in the winter, more like 7am - 10am and 8pm - 10pm in summer. The aim is to clear moisture out of the house. I have it off when it would the house too cold, too hot, or when the noise bothers me. They have filters which need to be cleaned every 3-6 months, which is why it'll be making a mess.

Open fires can make a house colder, as it draws cold air in and the hot air goes up the chimney. Enclosed ones can work well when they're going, but when they're off the hole in the ceiling for the chimney lets out heaps of heat. The most effective thing I've done to keep my house warm is to take out the fireplace, close and insulate the ceiling, and put a heat pump into that end of the house. I'd say without heating that room's 5 degrees warmer in the morning than it was when there was a fire in there.

From Nick Smiths paper on double glazing: - "This study found that the performance difference between double glazing and properly installed secondary glazing units to be minimal"

With regards to the original poster, where is the moisture in your house coming from please?

I personally think there needs to be far more information (and perhaps monitoring etc) around the concepts of home ventilation/heating/insulation. All three are required in a healthy home but they must be installed with consideration to the other two and the overall objectives for the home.

If you have a 1920's home then you typically have a bit of ventilation already around the windows, through the floors and under doors etc. Far more than a 1980's sealed aluminium joinery type house. If you are experiencing condensation then you're going to have to address where the water is coming from. Have you sealed the ground under the house with polyurethane sheeting? Are you sure the surrounding land doesn't slope down to the house? Do you have any leaking pipes, broken stormwater/drainage pipes etc? Do you have bathroom extraction fans? Do you use a clothes dryer that's not vented outside? Do you have a rangehood over the stove where you boil water in pots etc? etc?...

And leaving the supply side out of the equation, gas can be extremely similar to heat pump operating costs, and may be more suitable in temperate winter areas where the temperature is cold, but not quite cold enough for the water to 'drop' out of suspension as dew or a frost. The likes of Manawatu/Waikato etc may well fall into this category, whereby a heat pump will require a defrost cycle regularly. The cheapest form of heating is still firewood if you can source it yourself for free.

The condensation when we shifted in was, I believe, from a bathroom with no extraction, a faulty kitchen extractor, and very poor curtains in a mainly glass family room/kitchen area. Because the ventilation system had worked so well in our past house, we put one in, then fixed the extractor problems and have replaced curtains. In hindsight we should have done these things in the opposite order, as I'm pretty sure fixing extractors & curtains probably would have made a big difference on their own. With the old house, as we've found out, there is plenty of 'natural' ventilation around windows etc. We have taped up a lot of the gaps, but are intentionally leaving some very slight ones in each room so we don't end up with mildew as we did in our first house, which was sealed tightly with aluminium windows/doors while we were out all day. Under the house seems dry (where I can see it), the section is flat so am pretty sure there's no run off going through there. Underfloor insulation will be going in as soon as I've got 3 quotes to compare (hopefully within a week) - thanks for the recommendation Regs, I'm contacting them today. That should also make quite a difference.